A method for preparing self-dispersible water-based carbon black

Abstract

The present invention relates to the field of chemical industry. A method for preparing self-dispersible water-based carbon black comprises the following steps: step 1), primary oxidation: subjecting carbon black to oxidation reaction with a strong oxidant to obtain a first mixture; step 2), primary centrifugation: subjecting the first mixture obtained in step 1) to centrifugation to obtain a first precipitate; step 3), grinding: subjecting the first precipitate obtained in step 2) to grinding into a powder having a particle size not greater than 200 nm; step 4), secondary oxidation: subjecting the powder obtained in step 3) to oxidation reaction with a strong oxidant to obtain a second mixture; step 5), secondary centrifugation: subjecting the second mixture obtained in step 4) to centrifugation to obtain a second precipitate; step 6), neutralization treatment: subjecting the hydrogen on the carboxyl group of the second precipitate obtained in step 5) to neutralization treatment. The self-dispersible water-based carbon black obtained by the method of the present invention has good dispersibility and stability in water.

Description

Technical Field

[0001] The invention relates to the field of chemical industry, in particular to pigments. Background Art

[0002] Carbon black is a natural black pigment with excellent water resistance and weather resistance, and is usually used as black pigment ink. However, carbon black is a non-water-soluble particle. Although it can temporarily become very fine particles after stirring and grinding, it is not stable in water. Summary of the invention

[0003] The object of the present invention is to provide a method for preparing self-dispersible water-based carbon black to solve the above technical problems.

[0004] The technical problem solved by the present invention can be achieved by adopting the following technical solutions:

[0005] A method for preparing self-dispersible water-based carbon black, characterized in that it comprises the following steps:

[0006] Step 1), primary oxidation: subjecting carbon black to oxidation reaction with a strong oxidant to obtain a first mixture;

[0007] Step 2), primary centrifugation: centrifuging the first mixture obtained in step 1) to obtain a first precipitate;

[0008] Step 3), grinding: grinding the first precipitate obtained in step 2) into a powder with a particle size not greater than 200 nm;

[0009] Step 4), secondary oxidation: the powder obtained in step 3) is oxidized by a strong oxidant to obtain a second mixture;

[0010] Step 5), secondary centrifugation: centrifuging the second mixture obtained in step 4) to obtain a second precipitate;

[0011] Step 6), neutralization treatment: neutralizing the hydrogen on the carboxyl group of the second precipitate obtained in step 5).

[0012] Preferably, the specific surface area of ​​the carbon black in step 1) is 300 m 2 / g-500m 2 / g.

[0013] Preferably, the strong oxidant in step 1) and step 3) is hypochlorite.

[0014] Effective effect: The self-dispersible water-based carbon black obtained by the method of the present invention has good dispersibility and stability in water. DETAILED DESCRIPTION

[0015] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further described below.

[0016] A method for preparing a self-dispersible water-based carbon black, comprising the following steps: Step 1), primary oxidation: subjecting carbon black to an oxidation reaction with a strong oxidant to obtain a first mixture. Step 2), primary centrifugation: subjecting the first mixture obtained in step 1) to centrifugation to obtain a first precipitate. Step 3), grinding: subjecting the first precipitate obtained in step 2) to grinding into a powder having a particle size of no more than 200 nm. Step 4), secondary oxidation: subjecting the powder obtained in step 3) to an oxidation reaction with a strong oxidant to obtain a second mixture. Step 5), secondary centrifugation: subjecting the second mixture obtained in step 4) to centrifugation to obtain a second precipitate. Step 6), neutralization treatment: adding an alkali to neutralize the second precipitate obtained in step 5). Specific embodiments

[0018] Step 1), primary oxidation: The carbon black is oxidized with a strong oxidant to obtain a first mixture. Carbon blacks with different surface areas are oxidized with hypochlorite, the effective chlorine content of the hypochlorite is 12%, and the molar ratio of the carbon black to the strong oxidant is 1:0.4-0.8. The oxidation reaction temperature is about 40°C, and the time required for oxidation is recorded, as shown in the following table:

[0019]

[0020] According to the above table, when the specific surface area of ​​carbon black is 300m 2 / g-500m 2 / g, the oxidation time is ideal, so the specific surface area of ​​carbon black is preferably 300m 2 / g-500m 2 / g. At the same time, it was also found that as the specific surface area of ​​carbon black decreases, the carbon black particles become larger and the time required for oxidation increases. However, when the specific surface area increases to a certain extent, the aggregation of carbon black will gradually become more serious, which will cause the time required for oxidation to increase instead of decrease.

[0021] Another surface area of ​​400m 2 / g of carbon black, different effective chlorine contents were selected, and the oxidation efficiency was tested at different reaction temperatures. After testing and optimization, the effective chlorine of hypochlorite was 10%-15%, the temperature during the oxidation reaction was 40-60°C, and as the temperature rose, the reaction time was in the range of 0.5-1.8 hours.

[0022] Therefore, the present invention further prefers that the specific surface area of ​​carbon black is 300m 2 / g-500m 2 / g, the available chlorine of hypochlorite is 10%-15%, the temperature during oxidation reaction is 40-60°C, and the reaction time is 1.5-2 hours, which is convenient for mechanized control during industrial mass production.

[0023] The oxidation here refers to oxidation to an oxygen content of 6-12%, and the oxygen content can be tested using Thermo Fisher's FlashSmart elemental analyzer.

[0024] The chemical reaction formula of the main chemical reaction occurring during the oxidation process is:

[0025] C-H+M(ClO) x →C-COOM, where M is a metal ion.

[0026] Step 2), primary centrifugation: centrifuge the first mixture obtained in step 1) to obtain a first precipitate.

[0027] Step 3), grinding: Grind the first precipitate obtained in step 2) into a powder with a particle size not greater than 200nm. Grinding can be performed by a grinder. Preferably, the rotation speed of the grinder is 3000-4000rpm, and the grinding time is 2-6 hours. Preferably, 0.2-0.4mm zirconium beads are added to the grinding chamber of the grinder. The present invention selects grinding materials. The material is selected as zirconium, and the zirconium beads are strong and wear-resistant, have a long service life, and will not drop powder into the grinded object, thereby ensuring the purity of the grinded object. The size is selected to be 0.2-0.4mm, so that the gap between the zirconium beads is sufficient to grind the grinded object to a particle size of 90-120nm.

[0028] Step 2) After centrifugal separation, the surface of the carbon black carries water, and the carbon black carrying water can be directly put into the grinder as the first precipitate. The carbon black carrying water can also be dried first, and the dried carbon black can be put into the grinder as the first precipitate. Preferably, the present invention directly puts the carbon black carrying water into the grinder as the first precipitate. In the initial stage of grinding, the water on the first precipitate acts as a refrigerant, which can cool the grinder and zirconium beads. During the grinding process, the water on the first precipitate evaporates, which also plays a role in driving the movement of the carbon black powder, thereby improving the grinding efficiency.

[0029] Step 4), secondary oxidation: the powder obtained in step 3) is subjected to oxidation reaction with a strong oxidant to obtain a second mixture. The present invention can effectively reduce the particle size of carbon black by two oxidations, solving the problem that the carbon black cannot meet the particle size requirement after only one oxidation (the particle size after one oxidation is about 150-200nm, which is too large).

[0030] The oxidation here refers to oxidation to an oxygen content of 10-16%, and the oxygen content can be tested using Thermo Fisher's FlashSmart elemental analyzer.

[0031] The particle size of the powder obtained in step 3) is relatively small. In order to ensure the oxidation efficiency, nitrogen can be introduced into the mixture of the powder and the strong oxidant to disperse the carbon black particles and reduce the aggregation of the carbon black particles. The strong oxidant in step 4) is preferably hypochlorite. The effective chlorine of hypochlorite is 10%-15%. The temperature during the oxidation reaction is 40-60°C and the reaction time is 0.5-2.0 hours. The molar ratio of powder to strong oxidant is preferably 1:0.3-0.6.

[0032] The strong oxidant used here is consistent with that used in step 1). Compared with using different strong oxidants, the storage cost and use cost of the strong oxidant can be effectively reduced, and the interaction of some substances between the two strong oxidants can be avoided, which is beneficial to improving production safety.

[0033] Step 5), secondary centrifugation: centrifuge the second mixture obtained in step 4) to obtain a second precipitate. The present invention can effectively remove inorganic salts and other impurities generated in the reaction process in the solution through two centrifugations.

[0034] Step 6), neutralization treatment: neutralize the hydrogen on the carboxyl group of the second precipitate obtained in step 5). Preferably, the hydrogen on the carboxyl group of the second precipitate is neutralized with a base. The base can be an inorganic base or an organic base, wherein the inorganic bases include: sodium hydroxide, lithium hydroxide, sodium potassium hydroxide, calcium hydroxide, magnesium hydroxide, sodium carbonate, potassium carbonate, lithium carbonate, magnesium carbonate, calcium carbonate, etc.; the organic bases include: methylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, monomethanolamine, dimethanolamine, trimethanolamine, monoethanolamine, diethanolamine, triethanolamine, etc. Preferably, the base is sodium hydroxide, lithium hydroxide, monoethanolamine, diethanolamine, triethanolamine

[0035] More preferably, after diluting the second precipitate obtained in step 5) with water, a base is added to neutralize the hydrogen on the carboxyl group. Diluting first and then neutralizing can effectively avoid the problem that the second precipitate is in a solid state and cannot be stirred evenly when a base is directly added.

[0036] After step 6), add water to a dispersion with a carbon black concentration of 12-15%. Water can be added directly in step 6) to a carbon black concentration of 12-15%. It can also be done by first adding a portion in step 6) and then adding water to a carbon black concentration of 12-15%. It is preferred to add water directly to speed up the reaction rate in step 6). While adding water, nitrogen is added. Nitrogen can impact carbon black, increase the degree of mixing between carbon black and alkali, accelerate the neutralization process, and improve the dispersion uniformity and stability of carbon black in water. The nitrogen here can be the nitrogen recovered after use in step 4). Nitrogen is also beneficial to reduce oxygen in the production environment and improve the safety of the production environment. The amount of water added can be calculated based on the mass of the original carbon black, that is, the mass ratio of carbon black in step 1) and water in step 6) is preferably 15:65-75, and further preferably 15:70. For example: if the mass of the original carbon black is 15g, then add 70g of water.

[0037] In step 4) and step 6), it is not recommended to use a stirring device to improve efficiency, so as to avoid the powder on the stirring device from mixing into the carbon black, thereby improving the purity of the carbon black. Nitrogen is used instead of the stirring device.

[0038] The dispersion of carbon black is reflected by the change of particle size, so the dispersion and stability of carbon black can be judged by measuring the average particle size. The following samples were prepared according to the methods in the table.

[0039]

[0040] The following is a HORIBA SZ-100 particle size analyzer to measure the changes in the average particle size of the above four samples. The test results are as follows:

[0041]

[0042] According to the above table, we can see that:

[0043] 1. The performances of the four samples obtained by the method of the present invention are relatively stable.

[0044] 2. Introducing nitrogen in step 4) and step 6) can improve the dispersibility of carbon black.

[0045] 3. Sample 1 is the best sample.

[0046] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for preparing self-dispersible water-based carbon black, characterized in that: The steps include: Step 1), primary oxidation: oxidizing carbon black with a strong oxidant to obtain a first mixture, wherein the molar ratio of carbon black to the strong oxidant is 1:0.4-0.8; Step 2), primary centrifugation: centrifuging the first mixture obtained in step 1) to obtain a first precipitate; Step 3), grinding: grinding the first precipitate obtained in step 2) into a powder with a particle size not greater than 200 nm; Step 4), secondary oxidation: the powder obtained in step 3) is oxidized by a strong oxidant to obtain a second mixture, and nitrogen is introduced into the mixture of the powder and the strong oxidant; Step 5), secondary centrifugation: centrifuging the second mixture obtained in step 4) to obtain a second precipitate; Step 6), neutralization treatment: neutralize the hydrogen on the carboxyl group of the second precipitate obtained in step 5), add water to a dispersion with a carbon black concentration of 12-15%, and add nitrogen while adding water; Wherein, after the centrifugal separation in step 2), the surface of the carbon black carries water, and the carbon black carrying water is directly used as the first precipitate and put into the grinder; Wherein, step 4) and step 6) are stirred without stirring device.

2. The method for preparing a self-dispersible aqueous carbon black according to claim 1, characterized in that: The specific surface area of ​​the carbon black in step 1) is 300 m 2 / g-500m 2 / g.

3. The method for preparing a self-dispersible aqueous carbon black according to claim 2, characterized in that: The strong oxidant in step 1) and step 3) is hypochlorite.

4. The method for preparing a self-dispersible aqueous carbon black according to claim 3, characterized in that: The effective chlorine content of the hypochlorite in step 1) is 10%-15%, the molar ratio of carbon black to strong oxidant is 1:0.4-0.8, the oxidation reaction temperature is 40°C-60°C, and the reaction time is 1.5-2 hours.

5. The method for preparing a self-dispersible aqueous carbon black according to claim 3, characterized in that: The available chlorine of the hypochlorite in step 4) is 10%-15%, the molar ratio of the powder to the strong oxidant is 1:0.3-0.6, the temperature during the oxidation reaction is 40-60°C, and the reaction time is 0.5-2.0 hours.

6. The method for preparing a self-dispersible aqueous carbon black according to claim 1, characterized in that: In step 3), the grinding is performed by a grinder, the rotation speed of the grinder is 3000-4000 rpm, and the grinding time is 2-6 hours.

7. The method for preparing a self-dispersible aqueous carbon black according to claim 6, characterized in that: Add 0.2-0.4 mm zirconium beads into the grinding chamber of the grinder.

8. The method for preparing a self-dispersible water-based carbon black according to claim 1, characterized in that: After the second precipitate obtained in step 5) is diluted with water, a base is added to neutralize the hydrogen on the carboxyl group.

9. The method for preparing a self-dispersible water-based carbon black according to claim 1, characterized in that: The mass ratio of the carbon black in step 1) to the water in step 6) is 15:65-75.

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